Occupational upper extremity trauma is an extremely common, yet under-studied problem with few published case-control studies in the literature. In 1996 there were 1.4 million emergency department visits for occupational upper extremity trauma, 80% of which involved the fingers, hand or wrist. Approximately 500,000 work-related finger or hand lacerations were treated in emergency departments nationwide. Furthermore, occupational upper extremity truma accounted for 23% of all lost work day cases reported to the Bureau of Labor Statistics in 1996. Despite the public health importance of these injuries, relatively little is known about potentially preventable transient etiologic factors that immediately precede them. The recently developed case-crossover methodology is ideally suited to study such transient exposures. In this application, we propose to conduct a case-crossover study of 1,000 work-related hand injury patients recruited from 22 occupational health clinics in the New England area over a 2 year period. We will investigate the association between workplace factors and occupational traumatic injury to the hand and fingers. We will evaluate risk factors in the following domains: (1) Work equipment factors including unusual performance of equipment or tools and the use of gloves; (2) Work practices such as performing an uncommon work task or using an unusual work method; (3) worker-related factors including fatigue, feeling ill, being rushed, and being distracted. In addition, we will evaluate industrial sector, specific occupation and worker characteristics including gender, age, handedness, job experience, race/ethnicity, and hand injury history as modifiers of the relative risks observed. In a pilot study using the proposed study protocol, we successfully telephone interviewed 130 patients (70% of those eligible) with occupational traumatic injury to the fingers or hand. In 66% of cases, the interview was conducted within 1 day of the injury. Patients primarily represented manufacturing, construction and service industries. Among our preliminary findings, we observed a 5.8 fold increase in risk of occupational traumatic injury to the fingers or hand (95% CI: 3.9 to 8.6) when using an unusual work method compared to standard work practices. Successful completion of this study will identify potentially modifiable factors that increase the risk of occupational hand injury. This knowledge will facilitate the development of specific interventions designed to reduce the incidence of these injuries.